Mechanical diverter

ABSTRACT

An apparatus for performing a wellbore operation includes a retrievable tubular defining an axial flowbore and having at least one opening providing fluid communication between the flowbore and a formation, and a degradable diverter disposed at least partially in an annulus between a wellbore and the retrievable tubular, and adjacent to the at least one opening. The degradable diverter comprises a material that structurally degrades over an engineered time interval in response to an applied stimulus. The degradable diverter also directs a stimulation fluid exiting through the at least one opening towards the formation. The degradable diverter is connected to the retrievable tubular, a stimulation fluid is pumped through the flowbore. It is emphasized that this abstract is provided to comply with the rules requiring an abstract, which will allow a searcher or other reader to quickly ascertain the general subject matter of the technical disclosure.

BACKGROUND OF THE DISCLOSURE

1. Field of the Disclosure

This disclosure relates generally to oilfield downhole tools and more particularly to methods and devices for directing a stimulation fluid into the formation using a retrievable tubular.

2. Description of the Related Art

As the oil and gas industry continues to explore and produce from wells that are deeper, designing downhole tools that can operate in sequential zone completion and intervention becomes a challenge. Stimulating certain formation zones with tools and retrieving those tools in a deep well environment can be difficult if subterranean tools such as packers malfunction. Of particular concern are malfunctions that prevent a packer used during stimulation operations from being retrieved from the well. In such instances, the packers, including retrievable packers, may require milling or other additional well intervention operations to obtain the desired wellbore cross-sectional area.

In some aspects, the present disclosure is directed to methods and devices for assisting stimulation operations that are not susceptible to such malfunctions.

SUMMARY OF THE DISCLOSURE

In one aspect, the present disclosure provides a downhole tool for performing a wellbore operation. The downhole tool may include a retrievable tubular defining an axial flowbore and having at least one opening providing fluid communication between the flowbore and a formation. The downhole tool may also have a degradable diverter disposed at least partially in an annulus between a wellbore and the retrievable tubular, and adjacent to the at least one opening. The degradable diverter comprises a material that structurally degrades over an engineered time interval in response to an applied stimulus. The degradable diverter directs a stimulation fluid exiting through the at least one opening towards the formation.

In another aspect, the present disclosure provides a method for performing a wellbore operation. The method may include connecting a degradable diverter to a retrievable tubular defining an axial flowbore and having at least one opening providing fluid communication between the flowbore and a formation. The degradable diverter is disposed at least partially in an annulus between a wellbore and the retrievable tubular, and adjacent to the at least one opening. The method may also include pumping a stimulation fluid through the flowbore, allowing the stimulation fluid to exit through the at least one opening, directing the stimulation fluid towards the formation using the degradable diverter; and structurally degrading the degradable diverter over an engineered time interval using an applied stimulus.

Illustrative examples of some features of the disclosure thus have been summarized rather broadly in order that the detailed description thereof that follows may be better understood, and in order that the contributions to the art may be appreciated. There are, of course, additional features of the disclosure that will be described hereinafter and which will form the subject of the claims appended hereto.

BRIEF DESCRIPTION OF THE DRAWINGS

For detailed understanding of the present disclosure, references should be made to the following detailed description of the preferred embodiment, taken in conjunction with the accompanying drawings, in which like elements have been given like numerals and wherein:

FIG. 1A shows an exemplary retrievable tubular and degradable diverters in a wellbore according to the present disclosure;

FIG. 1B shows an exemplary wellbore after the retrievable tubular is retrieved;

FIG. 2A-D show axial cross-sections of exemplary degradable diverters;

FIG. 3A-C show axial cross-sections of exemplary degradable diverters with sliding engagements; and

FIG. 4 shows an exemplary degradable diverter formed as a swab cup.

DETAILED DESCRIPTION OF THE DISCLOSURE

The present disclosure relates to devices and methods for well stimulation operations using a retrievable well stimulation system. The well stimulation system directs a stimulation fluid through a tubular into the formation. Degradable flow diverters anchor the tubular in the well and assist in directing the stimulation fluid from openings in the tubular into the formation. The degradable flow diverters are engineered to structurally degrade when exposed to one or more selected fluids. When the diverter structurally degrades, the anchoring effect diminishes until the downhole tubular becomes free. Now, the tubular can be retrieved, which opens the bore for further stimulation/intervention operations or for deployment of other tools.

FIG. 1A shows one non-limiting embodiment of a degradable diverter 50 used in connection with a bottom hole assembly (BHA) 9. The BHA 9 may be a completion assembly adapted for a well stimulation operation at a target depth in a wellbore 12. The BHA 9 may be run in on a casing, liner, tubing, coiled tubing or other suitable tubular 10. Well stimulation fluids pumped from the surface exit the tubular 10 via one or more axially spaced-apart openings 40 formed in the tubular 10. The degradable diverters 50 attached to the BHA 9 direct the exiting well stimulation fluid toward the adjacent formation.

The degradable diverters 50 may be radially projecting members that confine the fluid exiting the openings 40 to a radial flow direction. In one embodiment, each degradable diverter 50 may include a first element 50 a and a second element 50 b. The openings 40 can be located between the first element 50 a and the second element 50 b. When landed at the target depth, the degradable diverters 50 a,b bracket the perforations 16 and thereby direct stimulation fluid through the perforations 16 and into the formation.

The diverters 50 are referred to as “degradable” because they are at least partially formed of a material that can undergo an irreversible change in its structure. Herein, “degradable” means disintegrable, corrodible, decomposable, soluble, etc. Examples of suitable materials and their methods of manufacture are given in United States Patent Publications No. 2013/0025849 (Richard and Doane) and 2014/0208842 (Miller et al.), and U.S. Pat. No. 8,783,365 (McCoy and Solfronk), which Patent Publications and Patents are hereby incorporated by reference in their entirety. A structural degradation may be a change in phase, dimension or shape, density, material composition, volume, mass, etc. The degradation may also be a change in a material property; e.g., rigidity, porosity, permeability, etc. Also, the degradation occurs over an engineered time interval; i.e., a predetermined time interval that is not incidental. Illustrative time intervals include minutes (e.g., 5 to 55 minutes), hours (1 to 23 hours), or days (2 to 3 or more days).

The degradable diverters 50 can be high-strength and lightweight, and have fully-dense, sintered powder compacts formed from coated powder materials that include various lightweight particle cores and core materials having various single layer and multilayer nanoscale coatings. These powder compacts are made from coated metallic powders that include various electrochemically-active (e.g., having relatively higher standard oxidation potentials) lightweight, high-strength particle cores and core materials, such as electrochemically active metals, that are dispersed within a cellular nanomatrix formed from the various nanoscale metallic coating layers of metallic coating materials, and are particularly useful in borehole applications.

Suitable core materials include electrochemically active metals having a standard oxidation potential greater than or equal to that of Zn, including as Mg, Al, Mn or Zn or alloys or combinations thereof. For example, tertiary Mg—Al—X alloys may include, by weight, up to about 85% Mg, up to about 15% Al and up to about 5% X, where X is another material. In one embodiment, the material has a substantially uniform average thickness between dispersed particles of about 50 nanometers (nm) to about 5000 nm. In one embodiment, the coating layers are formed from Al, Ni, W or Al₂O₃, or combinations thereof. In one embodiment, the coating is a multi-layer coating, for example, comprising a first Al layer, a Al₂O₃ layer and a second Al layer. In some embodiments, the coating may have a thickness of about 25 nm to about 2500 nm. In addition, surface irregularities to increase a surface area of the degradable diverter 50, such as grooves, corrugations, depressions, etc. may be used.

The degradable diverter 50 may also be made of phenolics, polyvinyl alcohols, polyacrylamide, polyacrylic acids, rare earth elements, glasses (e.g. hollow glass microspheres), carbon, elastic material, or a combination of these materials or above sintered powder compact material. Elastic material herein includes elastomers and means that the degradable diverter can flex.

As noted above, the degradation is initiated by exposing the degradable material to a stimulus. In embodiments, the degradable diverter 50 degrades in response to exposure to a fluid. Illustrative fluids include engineered fluids (e.g., frac fluid, acidizing fluid, acid, brine, water, drilling mud, etc.) and naturally occurring fluids (e.g., hydrocarbon oil, produced water, etc.). The fluid used for stimulus may be one or more liquids, one or more gases, or mixtures thereof. In other embodiments, the stimulus may be thermal energy from surrounding formation. Thus, the stimulus may be engineered and/or naturally occurring in the well or wellbore 12 and formation.

It should be understood that the degradable diverter 50 does not need to seal against an adjacent surface (e.g., casing wall or borehole wall). Rather, at least some circumferential portions of the degradable diverter 50 may have an engineered gap with the adjacent surface. During stimulation operations, solid particles such as sand, proppant or debris in the stimulation fluid or surroundings of the tubular 10 may plug the gap between the outer surface 60 (shown in FIGS. 2A-D) of the degradable diverter 50 and the wellbore 12.

These solid particles can create an anchoring effect for the tubular 10 to secure itself on the wellbore 12. In such instances, the stimulation fluid may be effectively prevented from leaking into surrounding the annular spaces. In instances that the gap is not plugged by the solid particles, fluid can escape through the gap to the annulus between the tubular 10 and the wellbore 12. However, this fluid leakage is insignificant compared to the flow through the openings 40 since the pressure of the stimulation fluid is in the order of thousands of pounds per square inch.

An illustrative operation of the BHA 9 and the degradable diverters 50 will be discussed with reference to FIGS. 1A and 1B.

First, the tubular 10 is conveyed into the wellbore 12 until the BHA 9 and degradable diverters 50 are deployed at the target depth as shown in FIG. 1A. Next, the stimulation operation begins by pumping stimulation fluid through the tubular 10. As this fluid exits through the openings 40, the degradable diverters 50 channel flow in a radial direction into the perforations 16 and/or the formation. For the most part, the degradable diverters 50 block stimulation fluid from flowing into the adjacent annuli between the wellbore 12 and the tubular 10. As discussed previously, some fluid may leak into the adjacent annular spaced via the gap separating the degradable diverter 50 and the adjacent walls. However, such leakage may diminish or stop as solids plug the gap.

After stimulation has been completed, the degradable diverters 50 may be degraded using one or more schemes. For example, the material making up the degradable diverters 50 may be selected to degrade when exposed to the stimulation fluid. In such instances, the degradation may begin immediately. In another instance, the degradable diverter 50 may include a material that degrades when contacted by a secondary surface-supplied fluid such as water. In such an instance, the secondary fluid may be pumped down to degraded the degradable diverters 50. In still other examples, the material of the degradable diverters 50 may degrade when subjected to thermal energy (e.g., ambient wellbore temperatures) or naturally occurring formation fluids (e.g., water or hydrocarbons). Of course, combinations of such stimuli may also be used to initiate the degrading of the degradable diverters.

FIG. 1B shows the wellbore 12 after the stimulation operation is completed and the degradable diverters are degraded. As noted above, the degrading process may be engineered to occur over a period of minutes, hours, or longer. At the conclusion of the degrading process, the degradable diverters 50 have undergone an irreversible structural change. Specifically, the outer dimensions of the degradable diverters 50 have decreased in size. Therefore, the tubular 10 is free from an anchoring effect caused by the degradable diverter 50 and can be retrieved from the well. After retrieval, the well obtains its full bore for future operations.

It should be understood that the teachings of the present disclosure are susceptible to numerous embodiments and variants. Certain non-limiting embodiments and variations of the degradable diverter 50 will be discussed with reference to FIGS. 2A-D, 3A-C and 4.

FIG. 2A shows an axial cross-section of one of the elements of the degradable diverter 50 that continuously and circumferentially surrounds the tubular 10. The degradable diverter 50 may be formed as a collar and have a chamfered rectangular axial cross-section. The degradable diverter 50 may be formed as a single body or as segmented assembly. As shown, the degradable diverter 50 may be fixed to the tubular 10. By fixed, it is meant to be prevented of axial or rotational movement. Alternatively, the degradable diverter 50 may be formed on a separate sub. The outer surface 60 of the degradable diverter 50 may rest against the wellbore 12, or may have a partial or complete gap with the wellbore 12 as discussed previously.

FIG. 2B-D show other shapes and configurations of the degradable diverter 50. FIG. 2B shows the degradable diverter 50 that has a triangular cross-section. FIG. 2C shows the degradable diverter 50 with a semi-circular cross section. FIG. 2D shows the cross section of the degradable diverter 50 defined by two concave arcs and an outer surface of the tubular 10. Other polygons, concave or convex shapes, and shapes defined by an arc, or a combination of these as axial cross sections can be used for the design of the degradable diverter 50.

The embodiments of FIGS. 2A-D have a generally fixed state (e.g., outer diameter) prior to the degrading process and a changed state after the degrading process (e.g., a reduced diameter). However, in other embodiments, states or conditions such as outer diameters can be adjustable before and during the degrading process.

FIG. 3A-C illustrate degradable diverters 50 that have adjustable outer diameters. Specifically, the diameters of the FIG. 3A-C diverters 50 can be increased to reduce the gap between the tubular 10 and the wellbore 12 in operation. The FIGS. 3A-C embodiments can be activated by hydrostatic or hydraulic pressure, or mechanical, acoustic, electrical or electromagnetic means. For simplicity, a hydraulic actuation will be used in the following discussion.

The FIG. 3A embodiment includes a diverter 50 that has two cooperating mating elements (mates) 52 a,b and 54 a,b that are initially fixed to one another with a locking device (not shown). The stimulation fluid exits from the opening 40, applies hydraulic pressure on the mates 52 a,b. Applied pressure shears the locking mechanism and moves the mates 52 a,b towards mates 54 a,b respectively. The mates 52 a,b move radially outward as the mates 52 a,b travel along the inclined surface of the mates 54 a,b. The mates 52 a,b may have slots or elastic or plastic properties to allow them shift radially outward. Before activation, the mates may have a clearance in between as shown by 52 a and 54 a, or may be in full contact on their respective inclined surfaces as shown by 52 b and 54 b as depicted in FIG. 3A.

FIG. 3B shows the mates 52 a,b as a ratchet mechanism that allows movement in one direction but prevents movement in the opposite direction. The movement increases the outer diameter of the degradable diverter 50. FIG. 3C shows the mates 52 a and 54 a as collet fingers that are adjustable to extend radially outward by a lever 64. The lever 64 may be attached to the mate 54 a or the tubular 10. A combination of above elements 50 a,b in FIGS. 2A-D and 3A-C may be used as the degradable diverters 50.

FIG. 4 shows the degradable diverter 50 with two elements 50 a,b as swap cups. The stimulation fluid can exit from the opening 40 and pressurize the volume 70. The stimulation fluid can extend the lips 72 radially outward and increase the outer diameter of the degradable diverter 50.

Thus, in the FIGS. 3A-4 embodiments, the degradable diverters 50 can have a reduced diameter while being conveyed into the wellbore 12 and then expand to a larger diameter during the stimulation operation. Still other variants and design arrangements are discussed below.

In some arrangements, the degradable diverters 50 may degrade at different times from each other during a single job due to their varying material content or in response to different stimuli. The degradable diverters 50 degrading at different times during an operation may enable selective zone fracing. The operation is not limited to fracing and may include well intervention, stimulation, or other wellbore operations.

In the above-described embodiments, a single diverter element 52 a,b is shown on either side of an opening 40. If desired, multiple degradable diverters 50 may be employed at each cluster of perforations 16. For example, two elements 50 a may be located on the uphole side of the opening 40 and two elements 50 b may be located on the downhole side of the opening 40. The uphole side of a structure means positioning closer to the surface, and downhole side means positioning closer to the bottom of the well with respect to the structure. The openings 40 may have only one slot or may have multiple slots arranged axially or circumferentially on the tubular 10.

In the above-described embodiments, the openings 40 are not blocked. If desired, the degradable diverter 50 may block the opening 40 until the portion blocking the opening degrades and diverts the fluid into the formation. Also, the opening 40 can be opened, unblocked, created and/or enlarged by some other part or method. Because the degradable diverter 50 can be tailored to completely degrade, for instance in about 4 to 10 minutes, the openings 40 can be opened, unblocked, created, and/or enlarged immediately as necessary or over a shorter or longer time period as necessary.

In FIGS. 1A-B, the tubular 10 is shown in a cased hole; i.e., the wellbore 12 includes a casing, or run in an open hole. The perforations 16 may have been created in the same run with the BHA 9 or in a previous run. The perforations 16 may be flow paths or other gateways into the formation such as fractures. However, the tubular 10 may also be run in an open hole wherein there is no casing and associated perforations. In that case, the degradable diverters 50 direct the injection of the stimulation fluid into the formation the openings 40 face.

As used above, “engineered” means that the configuration is in accordance with experimental and/or mathematically modeling. Based on such modeling, configuration, orientation, dimension and other design parameters of the BHA 9 including the degradable diverter 50 and the tubular 10 is determined.

The foregoing description is directed to particular embodiments of the present disclosure for the purpose of illustration and explanation. It will be apparent, however, to one skilled in the art that many modifications and changes to the embodiment set forth above or embodiments of different forms are possible without departing from the scope of the disclosure. It is intended that the following claims be interpreted to embrace all such modifications and changes. 

We claim:
 1. An apparatus for performing a wellbore operation, comprising: a retrievable tubular defining an axial flowbore and having at least one opening providing fluid communication between the flowbore and a formation; and a degradable diverter disposed at least partially in an annulus between a wellbore and the retrievable tubular, and adjacent to the at least one opening, wherein the degradable diverter comprises a material that structurally degrades over an engineered time interval in response to an applied stimulus, wherein the degradable diverter directs a stimulation fluid exiting through the at least one opening towards the formation.
 2. The apparatus of claim 1, wherein the degradable diverter comprises at least one of: (i) ceramics, (ii) phenolics, (iii) metals, (iv) polyvinyl alcohols, (v) polyacrylamide, (vi) polyacrylic acids, (vii) rare earth elements, (viii) glasses, and (ix) carbon.
 3. The apparatus of claim 1, wherein the degradable diverter has an axial cross section of at least one of: (i) a polygon, (ii) a concave shape, (iii) a convex shape, and (iv) defined at least partially by an arc.
 4. The apparatus of claim 1, wherein the degradable diverter has an engineered gap with a surface surrounding the degradable diverter.
 5. The apparatus of claim 1, wherein the degradable diverter comprises a swab cup.
 6. The apparatus of claim 1, wherein the degradable diverter has an adjustable outer diameter, the outer diameter expanding from a first diameter during run-in to a second larger diameter during operation.
 7. The apparatus of claim 6, wherein the degradable diverter comprises at least two mates, each mate having an inclined surface, wherein sliding engagement of the inclined surfaces expands the outer diameter of the degradable diverter.
 8. The apparatus of claim 6, wherein the degradable diverter expands to the second diameter when actuated by at least one of: (i) hydraulic actuator, (ii) mechanical actuator, (iii) hydrostatic pressure, (iv) electrical trigger (v) electromagnetic signal, and (vi) acoustic signal.
 9. The apparatus of claim 1, wherein the degradable diverter comprises a first and a second diverter element, the at least one opening being positioned between the first and the second diverter element.
 10. The apparatus of claim 1, wherein the at least one opening includes a plurality of axially spaced apart openings, and further comprising a plurality of degradable diverters disposed along the retrievable tubular, wherein each degradable diverter diverts the stimulation fluid from an adjacent axially spaced apart opening to the formation.
 11. The apparatus of claim 10, wherein at least two of the degradable diverters have at least one of: (i) a different axial cross section; and (ii) a different chemical composition.
 12. The apparatus of claim 10, wherein at least two of the degradable diverters are configured to degrade in response to different applied stimuli.
 13. The apparatus of claim 1, wherein the applied stimulus is one of: (i) temperature change (ii) the stimulation fluid, (iii) a wellbore fluid, and (iv) some other activation fluid applied for this purpose.
 14. The apparatus of claim 1, wherein the retrievable tubular is a part of a hydraulic fracture completion system.
 15. The apparatus of claim 1, wherein the material is a non-elastic material.
 16. A method for performing a wellbore operation, comprising: connecting a degradable diverter to a retrievable tubular defining an axial flowbore and having at least one opening providing fluid communication between the flowbore and a formation, wherein the degradable diverter is disposed at least partially in an annulus between a wellbore and the retrievable tubular, and adjacent to the at least one opening, pumping a stimulation fluid through the flowbore; allowing the stimulation fluid to exit through the at least one opening; directing the stimulation fluid towards the formation using the degradable diverter; and structurally degrading the degradable diverter over an engineered time interval using an applied stimulus.
 17. The method of claim 16, further comprising connecting a plurality of degradable diverters to the retrievable tubular and degrading at least two of the plurality of the degradable diverters at different times.
 18. The method of claim 17, wherein the at least two of the plurality of the degradable diverters are degraded using different fluid compositions.
 19. The method of claim 16, further comprising retrieving the retrievable tubular.
 20. The method of claim 16, wherein the retrievable tubular is part of a hydraulic fracture completion system. 